Abiotic stresses negatively impact the growth and development of plants and result in significant reductions in crop yield and quality. Abiotic stresses include excessive or insufficient light intensity, cold temperature resulting in freezing or chilling, warm or high temperature, drought, ozone, salinity, toxic metals, nutrient poor soils, and the like. Further, exposure to prolonged exposure to abiotic stresses results in a greater susceptibility to biotic stresses such as pathogens and pests. Mittler, R., Trends Plant Sci. 11:15-19 (2006).
Plants acclimate to particular stress conditions using responses that are specific for that stress. As an example, during drought conditions, a plant closes its stomata to reduce water loss. However, plants are often subjected to a combination of stresses. For example, drought conditions often are combined with excessive heat conditions. In contrast to response to drought, a plant's response to heat is to open stomata so that the leaves are cooled by transpiration. This conflict in response reduces a plants ability to naturally adjust to such stresses.
A number of methods for alleviating abiotic stress in plants have been developed and many are available commercially. Thus, for example, shade netting, mesh, or cloth can be used to alleviate excessive heat and light. The use of reflective fabric, such as metalized surface plastics, white plastics, and foil materials on the ground of an orchard or vineyard can result in an increase in fruit size and yield with a concomitant reduction in fruit sunburn damage resulting from exposure to abiotic stress. Fruit surface temperature can be reduced through the application of low volumes of water, which cools the fruit through evaporative cooling of the surrounding air. A further method for alleviating heat stress includes the use of reflective, particle film technology (PFT), such as the commercial products RAYNOX®, SUNSHIELD® and SURROUND®. Many of the available products and methods described above have serious shortcomings. As a consequence, additional methods and products are needed for alleviating the stress caused by abiotic factors.
The present invention overcomes previous shortcomings in the art by providing methods and compositions that increase the tolerance to abiotic stress in plants.